<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <style>
    .box {
      width: 1200px;
      height: 500px;
      margin: 0 auto;
      position: relative;
      background-color: red;
    }
    .abs {
      position: absolute;
      left: 100px;
      top: 100px;
      right: 100px;
      bottom: 100px;
      background-color: blue;
    }
  </style>
  <body>
    <div class="box">
      <div class="abs"></div>
    </div>
  </body>
</html>
